Technical Field
The present disclosure relates to a keyswitch device, a keyboard, and a membrane circuit board, and more particularly, to a keyswitch device, a keyboard, and a membrane circuit board capable of emitting light.
Description of Related Art
Currently, the keyboard is one of the indispensable input devices to enter text or numbers while using a PC. Moreover, consumer electronic products used in daily life or large-scale processing equipment used in the industrial sector all require key structure units input devices to operate.
In order to make it easier to use in dark places, LED (Light-Emitting Diode) keyboards have been developed on the market for users, so that diversity of keyboards has been increased. U.S. Publication No. 20040174339 discloses a conventional illuminated keyboard including a light guide element and LEDs additionally installed on the keyboard. Lights emitted by the LEDs enter the light guide element, so as to be guided and uniformly outputted or transmitted to the keycaps. Current computer products are developed to be light, thin, short, and small, and keyboards are no exception. Under this development trend, owing to installing the light guide element, the above-mentioned illuminated keyboard does not match the requirement of thickness.
U.S. Publication No. 20090223794 discloses another conventional illuminated keyboard using a circuit board for light guiding and disposing a reflective plate under the circuit board and light sources at a side of the circuit board, so that light emitted by the light sources are transmitted to the keycaps by the circuit board. Most of conventional illuminated keyboards supply power to LEDs through flexible circuit boards. For cost considerations, the conventional illuminated keyboards usually dispose the LEDs in a certain small area, so as to avoid using flexible circuit boards with large areas. However, the configuration makes the keyswitches proximal to the LEDs receive lights with higher intensities and the keyswitches distal to the LEDs receive lights with lower intensities. In this regard, certain light-reflecting portions must be disposed on the light guide element to compensate the differences of the intensities by complicated ways, but the light-reflecting portions provide less effect and increase the difficulty of design. Moreover, the light sources are independently disposed outside the circuit board, which is difficult to meet the requirements of being waterproof and dustproof and may affect the reliability. Furthermore, circuit layouts on a circuit boards are mostly performed by applying a silver paste on substrates, but the materials of the substrates may easily be corroded by the silver paste, and the circuit layouts may affect the efficiency of outputting light, so that the luminous efficiency of products are affected.
U.S. Publication No. 20130313093 discloses another conventional illuminated keyboard, in which LEDs are respectively disposed under all keyswitches (or certain keyswitches), and the LEDs are directly disposed on the membrane circuit board by silver circuits and emit lights toward the keycaps of the keyswitches. However, the design needs a large number of LEDs, which may increase costs and consume more electricity. In addition, the silver circuits have large and different impedances, which may cause the unevenness of luminosity of the LEDs and greatly reduce the light-emitting effect of the keycaps. Nevertheless, the above-mentioned design may confine the light-emitting regions at small areas of the keycaps, which also affect the user's visual experience.
Accordingly, how to provide a keyswitch device to solve the aforementioned problems becomes an important issue to be solved by those in the industry.